Political and corporate leaders have increasingly scant reason to plead ignorance as the reason for inaction on climate change. Scientists have issued new studies and warnings about the dire consequences of unchecked global warming. The British government’s chief science advisor, David King, is on record as saying that global warming is a far worse threat than terrorism. At a meeting of energy and environment ministers in Monterrey, Mexico, he warned that even if governments act now to curb carbon emissions, the world will nevertheless confront some 30 years of worsened floods, heatwaves, droughts, hurricanes, and a surge in infectious diseases.

But failure to act will bring far worse consequences—loss of food security, livelihoods, and habitats for millions of people in large areas of the Earth. Drought conditions will spread across half the planet’s land surface during this century. This conclusion emerges from a study by the Hadley Centre for Climate Prediction and Research, Britain's leading climate science establishment. The study, “Modelling the Recent Evolution of Global Drought and Projections for the 21st Century with the Hadley Centre Climate Model,” will be published October in The Journal of Hydrometeorology.

The study assesses drought, as measured by the so-called Palmer Drought Severity Index (PDSI), in the face of predicted changes in rainfall and heat as a result of climate change. The PDSI figure for moderate drought, currently affecting 25 percent of the Earth's surface, is predicted to rise to 50 percent by 2100. Severe drought would rise from 8 to 40 percent, and extreme drought from 3 to 30 percent. Thus, a third of the earth would become inhabitable due to the inability to maintain agricultural production. The Hadley Centre scientists stress that the study contains uncertainties, and that additional assessments are planned to more closely model the likely impacts on specific places on Earth. The study is a conservative estimation in that it did not include potential effects on drought from global-warming-induced changes to the Earth's carbon cycle. The effects will be most severe in developing countries, undermining agriculture and food security, reducing water availability, and handicapping sanitation systems. Hundreds of millions of people already eking out a meager living may get pushed over the precipice. Africa, already badly affected by drought and food emergencies, would likely see the worst impacts. But developed nations will not escape the consequences, either. The Northeast Climate Impacts Assessment—a collaboration between the Union of Concerned Scientists and a number of U.S. scientists—finds that if carbon emissions grow unchecked, the nine states in the U.S. Northeast could experience a rise in average summer temperatures of more than 12 degrees Fahrenheit by the year 2100. Under a lower emissions scenario, the increase would be between 3.5 and 6.5 degrees Fahrenheit. Northeastern cities would see 9 days over 100 degrees Fahrenheit under the lower emissions scenario by 2100, but 14-28 days under the high emissions path. Presently, they experience 1-2 such days. Other impacts include less snow in winter and more frequent drought, plus more frequent heavy rainfall.